@Data
@ExcelTarget("users")
public class User implements Serializable {
    //...
    @Excel(name = "爱好", width = 30.0, orderNum = "5")
    private List<String> hobbies;
}

@Data
@ExcelTarget("users")
public class User implements Serializable {
    
    // ......

    //    @Excel(name = "爱好", width = 30.0, orderNum = "5")
    @ExcelIgnore
    private List<String> hobbies;

    @Excel(name = "爱好", width = 30.0, orderNum = "5")
    private String hobby;

    public String getHobby() {
        StringBuilder builder = new StringBuilder();
        hobbies.forEach(e -> {
            builder.append(e).append("、");
        });
        return builder.substring(0, builder.length() - 1).toString();
    }
}

@Data
@ExcelTarget("cards")
public class Card implements Serializable {
    @Excel(name = "身份证号码", width = 20.0, orderNum = "6")
    private String number;
    @Excel(name = "籍贯", width = 40.0, orderNum = "7")
    private String address;
}

@Data
@ExcelTarget("users")
public class User implements Serializable {

    // ......
    @ExcelEntity // 标志对象之间
    private Card card;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@ExcelTarget("orders")
public class Order implements Serializable {
    @Excel(name = "订单编号", orderNum = "8", width = 20.0)
    private String no;
    @Excel(name = "订单名称", orderNum = "9", width = 15.0)
    private String name;
}

@Data
@ExcelTarget("users")
public class User implements Serializable {
    
    // ......
    @ExcelCollection(name = "订单列表", orderNum = "8") // 一对多
    private List<Order> orders;
}

@Data
@ExcelTarget("users")
public class User implements Serializable {

	// ......
    @Excel(name = "头像", type = 2, width = 20)// 2表示图像
    private String photo;
}

@Test
    public void bigDataExport() throws Exception {

        List<MsgClient> list = new ArrayList<MsgClient>();
        Workbook workbook = null;
        Date start = new Date();
        ExportParams params = new ExportParams("大数据测试", "测试");
        for (int i = 0; i < 1000000; i++) {  //一百万数据量
            MsgClient client = new MsgClient();
            client.setBirthday(new Date());
            client.setClientName("小明" + i);
            client.setClientPhone("18797" + i);
            client.setCreateBy("JueYue");
            client.setId("1" + i);
            client.setRemark("测试" + i);
            MsgClientGroup group = new MsgClientGroup();
            group.setGroupName("测试" + i);
            client.setGroup(group);
            list.add(client);
            if(list.size() == 10000){
                workbook = ExcelExportUtil.exportBigExcel(params, MsgClient.class, list);
                list.clear();
            }
        }
        ExcelExportUtil.closeExportBigExcel();
        System.out.println(new Date().getTime() - start.getTime());
        File savefile = new File("D:/excel/");
        if (!savefile.exists()) {
            savefile.mkdirs();
        }
        FileOutputStream fos = new FileOutputStream("D:/excel/ExcelExportBigData.bigDataExport.xlsx");
        workbook.write(fos);
        fos.close();
    }

Employee(id=0, name=小杰0, birthday=Wed Mar 30 19:42:54 CST 2022, age=10)
Employee(id=1, name=小杰1, birthday=Wed Mar 30 19:42:54 CST 2022, age=11)
Employee(id=2, name=小杰2, birthday=Wed Mar 30 19:42:54 CST 2022, age=12)
Employee(id=3, name=小杰3, birthday=Wed Mar 30 19:42:54 CST 2022, age=13)
Employee(id=4, name=小杰4, birthday=Wed Mar 30 19:42:54 CST 2022, age=14)
Employee(id=5, name=小杰5, birthday=Wed Mar 30 19:42:54 CST 2022, age=152)
Employee(id=6, name=小杰6, birthday=Wed Mar 30 19:42:54 CST 2022, age=16)
Employee(id=7, name=小杰7, birthday=Wed Mar 30 19:42:54 CST 2022, age=17)
Employee(id=8, name=小杰8, birthday=Wed Mar 30 19:42:54 CST 2022, age=18)
Employee(id=9, name=小杰9, birthday=Wed Mar 30 19:42:54 CST 2022, age=19)

@Slf4j
@Controller
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    // 导入Excel文件
    @RequestMapping("/import")
    public String importExcel(MultipartFile excelFile) throws Exception {
        log.info("文件名称: [{}]", excelFile.getOriginalFilename());

        // excel导入
        ImportParams params = new ImportParams();
        params.setTitleRows(1);
        params.setHeadRows(1);
        List<User> objects = ExcelImportUtil.importExcel(excelFile.getInputStream(), User.class, params);
        objects.forEach(System.out::println);
        userService.saveAll(objects);

        return "redirect:/user/findAll";
    }

    // 查询所有
    @RequestMapping("/findAll")
    public String findAll(Model model){
        List<User> users = userService.findAll();
        model.addAttribute("users", users);
        return "index";
    }
}

@Service
@Transactional
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDAO userDAO;

    // 查询所有
    @Override
    public List<User> findAll() {
        return userDAO.findAll();
    }

    // 导入Excel
    @Override
    public void saveAll(List<User> objects) {
        objects.forEach(user -> {
            user.setId(null);
            userDAO.save(user);
        });
    }
}

    // 导出Excel文件
    @RequestMapping("/export")
    public void exportExcel(HttpServletResponse response) throws Exception {
        // 查询所有数据
        List<User> users = userService.findAll();
        //导出excel
        response.setHeader("content-disposition", "attachment;fileName=" + URLEncoder.encode("用户列表.xls", "UTF-8"));
        ServletOutputStream outputStream = response.getOutputStream();
        Workbook workbook = ExcelExportUtil.exportExcel(new ExportParams("学生列表信息", "学生信息"), User.class, users);
        workbook.write(outputStream);
        outputStream.close();
        workbook.close();
    }